An Air-Rechargeable Zn Battery Enabled by Organic–Inorganic Hybrid Cathode

Highlights The excellent performance of MoS2/PANI cathode is due to better conductivity and desolvation shielding. The self-charging zinc battery was successfully assembled that achieve deep self-discharge and long cycle life. The quasi solid state battery and battery module have excellent performance and practicability. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-023-01023-7.

mol L −1 ), respectively. The two solutions were mixed together under strong stirring, then kept in an ice bath for 12.0 h. The resulting precipitation was collected and washed with deionized water for three times, and dried at 70 °C in a vacuum oven.
1.421 g thiourea and 0.724 g (NH4)6Mo7O24·4H2O were dissolved in deionized water (21.8 mL) and stirred vigorously for 30.0 min to get a homogeneous solution. After the mixture was transferred to a Teflon-lined stainless-steel autoclave, it was heated to 180 °C and kept for 24.0 h. The resulting product was filtered, washed several times by deionized water and ethanol, and finally dried at 70 °C in a vacuum oven.

S1.3 Synthesis of MoS2/PANI
1.0 mmol MoS2 and 5.0 mg PANI were added in 24.0 mL HCl solution (1.0 mol L −1 ). The solution was transferred into a plastic tube for probe sonication and the typical probe sonication lasted for 10.0 min. After the mixture was transferred to a Teflon-lined stainless-steel autoclave. Then, it was heated to 120 °C and kept for 18.0 h. The resulting precipitation was collected and washed with deionized water for three times, and dried at 70 °C in a vacuum oven. For comparison, MoS2/PANI with more (10.0 mg) or less (1.0 mg) PANI addition was also studied.

S1.4 Preparation of Zinc Nanoflakes
Zinc nanoflakes were prepared by an electrodeposition method. Specifically, electrodeposition was carried out at −0.70 V (vs. Zn/Zn 2+ ) employing Zn metal plate as the reference and counter electrodes, carbon cloth as the working electrode, and 2.0 M ZnSO4 solution as the electrolyte, respectively. The load of zinc nanosheet was about 5.0 mg cm -1 .

S1.5 Preparation of PAM-PEG Hydrogel
Firstly, 5.0 g acrylamide, 25.0 mg K2S2O8 and 3.0 mg N, N′-methylenebisacrylamide were sequentially added to 30.0 ml deionized water. Then the mixture was stirred for 1.0 h and injected into a glass mould, followed by heating in an oven at 75 °C for 1.0 h. Finally, the as-fabricated hydrogel film was immersed in 2.0 M aqueous Zn(CF3SO3)2 (The volume ratio of PEG-400 is 25.0%) solution for 12.0 h to achieve the equilibrated state.

S1.6 Materials Characterization
The morphology and microstructure of the products were characterized using scanning electron microscopy (SEM, FEI Nova NanoSEM 450) and transmission electron microscopy (TEM, FEI Titan G2 60-300). The structure and phase purity of the assynthesized products were revealed by X-ray diffraction (XRD, Rigaku X-ray diffractometer with Cu-Kα radiation). X-ray photoelectron spectrometry (XPS) analysis was carried out on an AXIS-ULTRA DLD-600W spectrometer. Raman measurements were carried out on a LabRAM HR800. Thermogravimetric analysis (TGA) was conducted using an STA-449F3 instrument in an air atmosphere from 25 to 700 °C with a heating rate of 10 °C min −1 . ICP-OES/MS was carried out on a Hermo Fisher iCAP PRO (OES).

S1.7 Electrochemical Measurements
The electrode was prepared by mixing the active materials (20.0 mg), acetylene black (2.50 mg) and poly(vinylidene fluoride) (PVDF) (2.50 mg) in 500 μL Nmethylpyrrolidinone (NMP) with a mass ratio of 8.0 : 1.0 : 1.0. The load of active material is about 1.0-1.4 mg cm -2 . 30 μm Zn metal foil was firstly washed with diluted hydrochloric acid for 3 min to remove the surficial oxide layer and then washed with deionized water and ethanol. The mass loading of cleaned Zn foil anode is about 21.2 mg cm -2 . Then, the obtained slurry was cast onto Ti foil and dried at 70 °C for 8.0 h. The electrochemical performances of electrodes and the quasi-solid zinc battery including cyclic voltammetry (CV), galvanostatic charge and discharge curves (GCD) and electrochemical impedance spectroscopy (EIS) were tested using the electrochemical workstation (AUT302N FRA2.V). The cycle life measurements and GITT were performed on a LAND-CT2001A battery workstation.

S1.8 Calculation Details
All the density functional theory (DFT) calculations were performed using the first principle plane-wave pseudopotential formulation as implemented in the Vienna Abinitio Simulation Package (VASP) code. The generalized gradient approximation (GGA) within Perdew-Burke-Ernzerhof (PBE) was utilized as exchange correlation functional. The structures were relaxed until the forces were less than 0.010 eV/Å, and the energy convergent standard was 10 -4 eV. The Monkhorst−Pack mesh of the supercell was set to 2×2×1. Climbing-image nudged elastic band (CI-NEB) method was used to calculate the activation barriers for Zn 2+ hopping.
The discharge specific capacity was calculated from the results of galvanostatic discharge curves by the following Eq. S1: * ∆ (S1) Where C is the specific mass capacity, I, ∆ and m are the discharge current, discharge time and the mass of cathode active materials, respectively.
The energy density and power density are evaluated by the following Eqs. S2 and S3: Where DE and DP are respectively the energy density and power density, ∆ and ∆ are respectively the discharging time and discharge specific capacity, I is the discharge current, V is the working voltage, is the mass of cathode active materials.
The capacity retention (CR) and coulomb efficiency (CE) are calculated by the following Eqs. S4 and S5: Where t  is the discharge time of different cycles and 0 t  is the discharge time of the initial cycle.
, where mB is the mass of the active material, MB is the molecular weight, VM is the molar volume, A is the total contact area between electrode and electrolyte, τ is the duration time of the current pulse, ΔEτ is the variation of the battery voltage, and ΔES is related to the change of steady-state voltage for the corresponding step.
The b reflects the charge storage mechanism. b = 1/2 represents the diffusion control process while b =1 indicates the capacitive process. The k1v and k2v 1/2 represent capacitive process and diffusion control process, respectively.   The electrochemical reaction kinetics of MoS2, PANI and MoS2/PANI were studied by electrical impedance spectroscopy (EIS). The resistance obtained from the equivalent circuit fit values is shown in Table S2. It is obvious that the PANI electrode shows the lowest intercept on the x-axis (internal resistance, Rs) and the smallest semicircle (charge transfer impedance, Rct). The Rs denoting equivalent series resistance and Rct denoting charge transfer resistance. In addition, the Rs and Rct of MoS2/PANI are a medium value. These results can be understood by the facts that the proper coating of conductive PANI of MoS2 can effectively increase the electrical conductivity and enhance electrochemical reaction kinetics.    Figure S24a shows the excellent rate capability of MoS2/PANI cathode in N2 (the specific capacity at 0.50, 1.00, 2.00, 3.00, 4.00, 5.00 and 10.00 A g -1 are 304. 98, 272.56, 233.23, 197.78, 163.48, 159.43 and 104.44 mAh g -1 , respectively). In addition, the MoS2/PANI cathode has higher cycle life and poorer specific capacity in N2 due to air recharging capability. The content of F element on the surface of Zn0.85-xMo/P electrode in the presence of air is much higher than that in the presence of N2, which is attributed to the formation of Znx+y(CF3SO3)2y(OH)2x. In addition, the Znx+y(CF3SO3)2y(OH)2x was observed in the presence of air (Fig. S34). These evidences prove that O2 and H2O combine to form OHwhen Zn0.85-xMo/P is air recharging. Then the generated OH-and extracted Zn 2+ combine with the adsorbed electrolyte ions (Zn 2+ and CF3SO3 2-) to form an amorphous trifluoride containing the layered dihydroxide Znx+y(CF3SO3)2y(OH)2x.